1. Field of the Invention
The present invention generally relates to an apparatus for removing particles, and more specifically, to an apparatus for removing particles for a processing device including a vacuum container unit in which a predetermined process is performed on a wafer carried in by a conveyer unit. As the processing device to which the present invention is applied, there is a sputtering apparatus for manufacturing electronic devices such as a semiconductor integrated circuit and a liquid crystal panel.
2. Description of the Prior Art
As electronic devices such as a semiconductor integrated circuit and a liquid crystal display panel become larger in size and the processing technique thereof becomes more microscopic, particles such as dust in atmosphere and fine grains in the liquid chemical during the manufacturing process influence the characteristics or yield of electronic devices significantly. Due to this, elimination of particles is a very important factor. For example, in the semiconductor integrated circuit, the distance between metal wires formed on the circuit requires design rule of about 0.2 μm to 0.1 μm and the processing technique to be more microscopic. In such a microscopic circuit, since the sizes of particles are as large as or larger than the distance between metal wires, yield (ratio of source material to product) is degraded when particles are adhered to the wafer causing short circuits.
For example, in a sputtering apparatus used in the manufacturing process of semiconductor integrated circuits, inert gas ions are generated in a vacuum container of high vacuum level and impacted on a target using electric field generated by applying voltage between the target and a wafer. Atoms broken out of the target material by the impacts are deposited on the wafer to form predetermined thin films. During the formation of the thin films, some of the atoms broken out of the target material by the impact are deposited not only on the wafer but also on a jig for fixing the wafer or around the jig. The target materials deposited on the portions other than the wafer are separated by the stress of the film as the deposition grows, to float in the vacuum container as particles. Moreover, abrasions of the conveyer unit for the wafer mounted in the vacuum container and other movable parts cause the generation of particles. Particles adhered on the wafer itself and carried into the vacuum container also exist.
As shown in FIG. 7, a film-forming device in which particles are removed using electrostatic force is disclosed in Japanese Patent Unexamined Publication JP-A 6-252066 (1994). The film-forming device includes a vacuum container 41, a plate support 42 mounted in the vacuum container, a particle-collecting plate 43, a charging means 44 for charging the particle-collecting plate 43, and a charging bar 45 which constitutes a portion of the charging means. The film-forming device also includes an exhaust port 46, a reaction gas introduction line 47, a cleaning gas introduction line 48, a valve 49 and others (not shown).
In accordance with the film-forming device, the particle-collecting plate 43 composed of electric conductor material is conveyed into the vacuum container 41 and disposed on a predetermined position of the plate support 42. The charging bar 45 which constitutes a part of the charging means 44 is then unfolded to contact and charge the particle-collecting plate 43. At the same time, gas is introduced into the vacuum container 41 through the cleaning gas introduction line 48 which joins the reaction gas introduction line 47, so that the particles blown off by the gas is adsorbed on the charged particle-collecting plate 43 by electrostatic force. The particle-collecting plate 43 to which particles had adsorbed is then conveyed out of the vacuum container 41. The particles in the device are eliminated in above-described manner. Wafers for forming devices are then conveyed into the vacuum container 41 to be subjected to film formation processes.
However, in the film-forming device disclosed in Japanese Patent Unexamined Publication JP-A 6-252066 (1994), gas is injected to blow off particles, which diffuses particles into the entire vacuum container. Since the area of the charged particle-collecting plate is smaller compared to that of inner wall of the vacuum container, the elimination of the entire diffused particles using only the particle-collecting plate is not enough. Moreover, since the charging electrode contacts the particle-collecting plate for charging, the surface of the particle-collecting plate may be damaged due to scratches, resulting in generation of additional particles.
In addition, since a mechanism for moving the charging bar is mounted through the wall of the vacuum container, the means for charging the particle-collecting plate is complex and large, and requires high installation costs. Moreover, the operating costs get higher since expensive gas for assisting combustion is used for dry cleaning.
In addition, since the film-forming process must be stopped for a long time while the particle-collecting plate adsorbs particles, the rate of operation is reduced.